The present invention relates to a stripping composition which can be used in particular in the construction field, especially for the stripping of external organic coatings, such as exterior waterproof coatings and thin films. Exterior waterproof coatings, with a rubbery appearance are impermeable to air, to oxygen, and to water vapour and are based on acrylic or styrene-acrylic polymers.
In the construction field, most paint strippers are based on methylene chloride with methanol added. They can be thickened with cellulose compounds and can comprise an inorganic filler.
However, there is an increasing search to replace methylene chloride because of its very high volatility and very high toxiousness. Replacement products for the synergistic methylene chloride-methanol mixture exist but they are generally much more expensive and form at least 90% by weight of the composition of the formulation. The remaining 10% are composed of a thickener (generally chosen from cellulose or acrylic derivatives), itself generally even more expensive than the solvents, and various additives: activator, surfactant or corrosion inhibitor.
A subject matter of the present invention is thus a stripping composition which can be used in particular in the construction field, especially for the stripping of exterior waterproof coatings and thin films, characterized in that it comprises:
(A) an least one dibasic ester,
(B) at least one dipolar aprotic solvent,
(C) at least one cosolvent, and
(D) a combination of softening agents.
The composition according to the invention can comprise, per 100 parts by weight of (A)+(B)+(C)+(D):
5 to 50, in particular 10 to 45, parts by weight of (A);
10 to 60, in particular 25 to 55, parts by weight of (B);
10 to 50, in particular 15 to 40, parts by weight of (C); and
0.3 to 10, in particular 3 to 10, parts by weight of (D).
The dibasic ester or esters (A) are shown in particular from aliphatic dibasic esters, in particular C1-C4 alkyl diesters of one or more C4-C6 aliphatic dibasic acids. Mention may in particular be made of dimethyl succinate, dimethyl glutarate, dimethyl adipate and their mixtures.
The dipolar aprotic solvents (B) are advantageously chosen from dimethyl sulphoxide, N-methodypryyolidone, propylene carbonate, dimethyl-formamide, acetonitrile, N-methylmorpholine, butyro-lactone and dimethylacetamide. Dimethyl sulphoxide and N-methylpyrrolidone are preferred.
The choice will preferably be made, as cosolvents (C), of monoalkoxybenzenes, such as anisole and phenetole. Use will very particularly be made of phenetole.
According to the present invention, the term xe2x80x9ccombination of softening agentsxe2x80x9d preferably denotes a mixture comprising the following compounds: an alkyl lactate, such as ethyl lactate or butyl lactate; trimethylcyclohexanone or isphorone, or cyclohexyl acetate; an ethanolamine, such as monoethanolamino or diethanolamine, or methyldiethenaolamine; 1,2- or 1,3- or 1,4-dimethoxybenzene and water.
Each softening agent can be used in a proportion of at least 0.05 part by weight and preferably 0.5 part by weight per 100 parts by weight of (A)+(B)+(C)+(D).
The stripping composition according to the invention can additionally comprise:
at least one inorganic filler with a thickening nature, in a proportion in particular of 20 to 60 parts by weight, in particular of 25 to 50 parts by weight, per 100 parts by weight of (A)+(B)+(C)+(D), and/or
at least one cellulose thickener, in a proportion in particular of 0.05 to 1.5 parts by weight, in particular of 0.5 to 1.1 parts by weight, per 100 parts by weight of (A)+(B)+(C)+(D); and/or
at least one dispersing agent, in a proportion in particular of 0.1 to 10 parts by weight, in particular of 0.5 to 2 parts by weight, per 100 parts by weight of (A)+(B)+(C)+(D).
The term xe2x80x9cinorganic filler with a thickening naturexe2x80x9d is understood to mean a natural or synthetic inorganic powder which can result in formulations for which the viscosity is of the order of 6 000 mPaxc2x7s at 20 revolutions/min or 2 000 mPaxc2x7s at 100 revolutions/min.
The inorganic filler or fillers generally have a mean particle size of between 0.1 and 200 xcexcm, more particularly between 1 and 100 xcexcm. A finer particle size makes it possible to obtain the same viscosity while using less filler, which is not economically desirable.
Mention may be made, as examples of inorganic fillers, or calcium carbonate, silica, calcium phosphite, calcium hydroxide (Ca(OH)2), clay or bentonite.
Mention may be made, as example of cellulose thickener, of Methocell 311, sold by Dow Chemical Co., the process for the preparation of which is disclosed in U.S. Pat. No. 3,388,082, entitled xe2x80x9cHydroxypropyl methyl cellulose ethersxe2x80x9d.
Mention may be made, as an example of a dispersing agent, of the acidic phosphoric ester of 2-ethylhexanol, sold by Ceca under the name Beycostat A081.
The stripping composition according to the invention can additionally comprise at least one agent which provides it with a pleasant smell, i.e. a perfume in a proportion in particular of 1 to 10 parts by weight per 100 parts by weight of (A)+(B)+(C)+(D).
The stripping composition of the invention has proved to be highly advantageous; this is because, after it has been applied and then left to act for a few tens of minutes, it is sufficient to shift the dry strips using a paint knife. Wet and sticky waste, which is always difficult to remove and to treat, is avoided and most of the time a clean substrate, such as a concrete or brick wall, is obtained.
In the foregoing and in the following examples, all temperatures are set forth uncorrected in degrees Celsius; and, unless otherwise indicated, all parts and percentages are by weight.
In these examples, the ingredients used are as follows:
Dibasic ester:
DBE=dibasic ester having the following composition: (as % by weight):
dimethyl adipate/dimethyl glutarate/dimethyl succinate: 15/62/23, sold by Rhxc3x4ne-Poulenc under the name RPDE.
Polar aprotic solvent: DMSO
Cosolvent: Phenetole
Softening agents: trimethylcyclohexanone, ethyl lactate, cyclohexyl acetate, water, diethanolamine and 1,4-dimethoxybenzene.
Additives:
Cellulose thickener=cellulose thickener sold by Dow Chemical Co. under the name Methocell 311,
Dispersing agent=acidic phosphoric ester of 2-ethyl-hexanol, sold under the name Beycostat A081.
CaHPO3=natural calcium phosphite, produced by Ceca.
In these examples, all the proportions cited are in parts by weight.